Plant-eater is not your average superhero. She’s a plant with human qualities, reduces pollution and eats unwanted plants. Minus the side effects, she does the job of pesticides and clears toxicity. Other super heroes envied her.
Bat-man is needed only in Gotham. So are Super-man and Spider-man in their respective cities. But Plant-eater was outsourced worldwide without comic or screenplay advertisements. Hulk didn’t eat her, he hated veg food. Nobody could harm Plant-eater. Saddened, she went away forever by rooting himself. She made the others promise, however, to help everybody and not just their cities. Thus formed the Justice League!
(Purely Fictional. And like our lives, the above post is purely for entertainment purposes)